Friction crutch tip



May 17,, 1966 A. A. SMITH FRICTION CRUTCH TIP Filed March 16, 1964INVENTOR. ALFRED A. 544/771 United States Patent 3,251,372 FRICTIONCRUTCH TIP Alfred A. Smith, 8277 Lakershim Blvd North Hollywood, Calif.Filed Mar. 16, 1%4, Ser. No. 352,219 Claims. (Cl. 135-64) This inventionrelates to a friction crutch tip for use on crutches and canes.

It is the primary object of the invention to provide a new and improvedcrutch tip which is safer because it provides greater friction betweenthe tip and the ground than the tips that are presently in use.

It is a more particular object of my invention to provide a tip in whichthe base or ground engaging portion of the tip includes a plurality ofseparate ground engaging members, each of which has edges which areadapted to take a separate grip upon the ground.

With my improved tip, the edges of a plurality of separate membersengage the ground both at the beginning of the crutch movement, when thetip first engages the ground and is subjected to impact and at the endof the crutch movement, before the tip leaves the ground and when it issubject to thrust from the user.

Another object of my invention is to provide a crutch tip which in itspreferred embodiment works equally well at any angle and in anydirection.

In essence, my invention contemplates a crutch tip hav-' ing apreferably flat ground engaging base which is divided into a pluralityof separate or separable sections-or segments, each of which has edgeswhich are adapted to engage the ground. Whenthe tip is flexed, theseparation of the segments is increased, thus increasing the frictionalengagement of the tip with the ground, the coeflicient of friction ofthe'tip thus being increased in relationship to the frictional need asindicated by the flexing of the tip. At the same time, means areprovided for limiting the separation of the segments to assure theirreturn to their normal positions and to prevent foreign matter frombeing trapped in the area between the segments.

It is accordingly among the objects of my invention to provide a new andimproved crutch tip having all of the advantages and benefits of thestructure set forth above and described in greater detail hereinafter inthis-specification.

My invention also comprises such other objects, advantages andcapabilities as will later more fully appear and which are inherentlypossessed by my invention.

While I have shown in the accompanying drawings preferred embodiments ofmy invention, it should be understood that the same are susceptible ofmodification and change without departing from the spirit of myinvention.

Referring to the drawings,

FIG. 1 is a side elevational view, partly broken away and shown insection, of one embodiment of my friction crutch tip;

FIG. 2 is a bottom plan view of the same;

FIG. 3 is a sectional view of a portion of the bottom of the crutch tipin use, showing the flexing of the lands and the independent frictionalengagement of their edges with the ground;

FIG. 4 is a bottom plan view of an alternative bottom configuration;

FIG. 5 is a bottom plan view showing an alternative annular ring 24 isalso left uncut.

Patented May 17, 1966 "Ice corrugated pattern of land which may be usedinstead of or in combination with a straight land.

A preferred embodiment which has been selected to illustrate myinvention comprises a crutch tip 10, which is preferably molded of asingle piece of rubber or other suitable resilient material. The crutchtip 10 has a thick circular base 11 at the bottom, above which is anintegrally formed elongated neck 12. Between the neck 12 and base 11,the crutch tip 10 is provided with an annular groove 13, which definesthe horizontal axis of bending movement of the neck 12 with respect tothe base 11.

The inside of the crutch tip 10 is provided ith an elongatedsubstantially cylindrical hollow crutch shaft receiving passage 14, theupper Walls of which are provided with alternating lands and grooves,which provide a secure grip around the bottom portion of the cylindricalcrutch shaft. The passage 14 has a flat circular bottom, upon which maybe mounted a circular metal disc 18, which acts to reduce the frictionalwear of the end of the crutch shaft on the bottom of the passage 14.

The bottom of the base 11 is preferably flat. It is provided with aplurality of narrow, deep, concentric grooves 20, which extend asubstantial distance upwardly into the base 11. The grooves 20 dividethe bottom of the base 11 into a plurality of concentric lands 21. Aplurality of radially directed ties 22 extend across the grooves 20,connecting the adjacent lands 21 and dividing each of the lands 21 intoa plurality of segments. The lower edges of the ties 22 are disposedslightly upwardly from the lower edges of the lands 21.

A circular plug 23 is left uncut at the center of the 'bottom19, to actas a limit and stop for the inward flexing movement of the segments ofthe lands 21. An outer The outer ring 24 contains the lands 21 andlimits the outward flexing movement of their segments.

A crutch tip of the type described may be molded as a single piece ofrubber, with all of the lands 21 and ties 22 being integral, as shown inFIGS. 1-4 of the drawings.

It should be noted that, regardless of the method used, the lowerportions of the lands must remain separate and must not be cemented orvulcanized to each other or to the base. The bottom edges must be leftfree to flex and provide the desired increased frictional engagementwith the ground when the tip is flexed. I

In use, my crutch tip functions in a manner completely ditferent fromany crutch tip now in use. Referring to FIG. 3 of the drawings, thetip10 is flexed as it first engages the ground, flexing the base 11 toseparate the lands 21 and bring the inner edge of each of the lands 21into engagement with the ground. The result is that the edge of each ofthe lands 21 forms an independent frictional engagement with the groundand the resistance of the tip to slipping is the summation of theseseparate frictional engagements.

When the crutch reaches a vertical position, the bottom of the base ishorizontal and the tip 10 then begins to flex in the opposite direction.This flexing acts to separate the lands 21 on the opposite side of thetip, so that their edges engage the ground and resist slippage whichmight be caused by the thrust against the tip 10 by the user during thelatter part of the crutch movement.

. The total amount of friction generated by the plurality of edges ofthe separate lands engaging the ground is substantially greater thanthat of a conventional clutch tip.

It should also be noted that the stabilizing ties 22 divide each of thelands 21 into a plurality of short arcuate segments, each of which canmove only to a limited degree. This prevents extreme separation of thelands 21, with consequent enlargement of the grooves 20. This isdesirable because it assures the prompt return of the lands to theirnormal positions and because it prevents the grooves from becoming soenlarged that foreign matter such as pebbles, bits of glass, etc., arepicked up from the ground and entrapped within the grooves. Suchentrapped particles can damage the tip and can also damage floors,carpets, etc.

A concentric circular pattern of the type shown in FIG. 2 of thedrawings is believed to be more advantageous because it provides auniform action regardless of the direction of movement of the crutchtip. It is possible, however, to use other patterns or configurationssuch as square, diamond, cross-hatch, or any other regular pattern. FIG.4, for example, shows a concentric square pattern of grooves 32 andlands 33. The lands and grooves may also be corrugated as well asstraight, as shown by the corrugated land 34 in FIG. 5 of the drawings.The essential feature is that the bottom of the base must be divided orseparated into a plurality of segments, each of which has an edge orportion thereof which provides a separate frictional engagement with theground when the tip is flexed.

It will be noted that my friction crutch tip does not depend uponsuction for any of its ground gripping ability. Such suction tends to beeffective mainly at the midportion of the crutch action cycle, when itis actually least needed. The suction is also destroyed as soon as theedge of the crutch tip is worn sufficiently to permit air to enter thesuction area.

As shown in FIG. 3 of the drawings, each of the lands 21 has a pair ofstraight sides defined by the adjacent grooves 20 and a flat bottom,which forms a part of the flat ground engaging bottom portion of thebase 11. Each of the lands 21 accordingly has a pair of substantiallyright angular edges which, upon pivotal flexing movement of the crutchtip 10, flexes into simultaneous but independent engagement with theground. The frictional resistance of the bottom of the base 11 toslippage comprises the summation of the simultaneous frictionalengagements of the edges of the lands 21 with the ground.

I claim:

1. In a friction crutch tip, a base, the ground engaging bottom surfaceof said being substantially fiat and having a plurality of narrowconcentric circular grooves extending a substantial distance verticallyupwardly into said base from the bottom thereof, said grooves dividingsaid base into a plurality of separate concentric circular lands moldedintegrally with said base and separated from each other by said grooves,each of said lands being substantially Wider than said grooves, aplurality of ties molded integrally with said base, said ties extendingacross said grooves and joining said lands, each of said ties beingsubstantially equal in width to the width of said lands, said tiesextending from the top of said grooves to a point spaced slightlyupwardly from the bottom of said grooves, said ties dividing each ofsaid lands into a plurality of arcuate segments, said ties controllingthe flexing movement of said segments and preventing excessiveenlargement of said grooves, a circular center plug disposed adjacentthe center of the bottom of said base, and an annular outer ringextending around the periphery of the bottom of said base, said centerplug and outer ring limiting the inward and outward flexing movements of7 said lands, each of said lands having straight sides and a flat bottomdefining a pair of substantially right angular edges, the correspondingedges of a plurality of said lands being adapted to engage the groundindependently but simultaneously when said base is flexed upon thepivotal movement of said crutch tip, the frictional resistance of thebottom of said base to slippage comprising the summation of thesimultaneous frictional engagements of the edges of said lands with theground.

2. In a friction crutch tip, a base, the ground engaging bottom surfaceof said base being substantially flat and having a plurality of narrowconcentric circular grooves extending a substantial distance verticallyupwardly into said base from the bottom thereof, said grooves dividingsaid base into a plurality of separate concentric circular lands moldedintegrally with said base and separated from each. other by saidgrooves, each of said lands being substantially wider than said grooves,a plurality of ties molded integrally with said base, said tiesextending across said grooves and joining said lands, said ties dividingeach of said lands into a plurality of arcuate segments, said tiescontrolling the flexing movement of said segments and preventingexcessive enlargement of said grooves, and an annular outer ringextending around the periphery of the bottom of said base, said outerring limiting the outward flexing movement of said lands, each of saidlands having straight sides and a flat bottom defining apair ofsubstantially right angular edges, the corresponding edges of aplurality of said lands being adapted to engage the ground independentlybut simultaneously when said base is flexed upon the pivotal movement ofsaid crutch tip, the frictional resistance of the bottom of said base toslippage comprising the summation of the simultaneous frictionalengagement of the edges of said lands with the ground.

3. In a friction crutch tip, a base, the ground engaging bottom surfaceof said base being substantially flat and having a plurality of narrowconcentric circular grooves extending a substantial distance verticallyupwardly into said base from the bottom thereof, said grooves dividingsaid base into a plurality of separate concentric circular landsseparated from each other by said grooves, each of said lands beingsubstantially wider than said grooves, a plurality of ties extendingacross said grooves and joining said lands, said ties dividing saidlands into a plurality of arcuate segments, said ties controlling theflexing movement of said segments and preventing excessive enlargementof said grooves, each of said lands having straight sides and a flatbottom defining a pair of substantially right angular edges, thecorresponding edges of a plurality of said lands being adapted to engagethe ground independently but simultaneously when said base is flexedupon the pivotal movement of said crutch tip, the frictional resistanceof the bottom of said base to slippage comprising the summation of thesimultaneous frictional engagements of the edges of said lands with theground.

4. In a friction crutch tip, a base, the ground engaging bottom surfaceof said base being substantially flat and having a plurality ofconcentric narrow grooves extending a substantial distance verticallyupwardly into said base from the bottom thereof, said grooves dividingsaid base into a plurality of separate concentric lands separated fromeach other by said grooves, a plurality of ties extending across saidgrooves and joining said lands, said ties dividing said lands into aplurality of arcuate segments, said ties controlling the flexingmovement of said segments and preventing excessive enlargement of saidgrooves, each of said lands having a pair of edges, the correspondingedges of a plurality of said lands being adapted to engage the groundindependently but simultaneously when said base is flexed upon thepivotal movement of said crutch tip, the frictional resistance of thebottom of said base to slippage comprising the summation of thesimultaneous frictional engagements of the edges of said lands with theground.

5. In a friction crutch tip, a base, the ground engaging bottom surfaceof said base having a plurality of narrow grooves extending asubstantial distance vertically upwardly into said base from the bottomthereof, said grooves dividing said base into a plurality of landsseparated from each other by said grooves, each of said lands having apair of edges, the corresponding edges of a plurality of said landsbeing adapted to engage the ground independently but simultaneously whensaid base is flexed upon the pivotal movement of said crutch tip, thefrictional resistance of the bottom of said base to slippage comprisingthe summation of the simultaneous frictional engagements of the edges ofsaid lands with the ground, and a plurality of ties extending acrosssaid grooves and joining said lands, said ties dividing said lands intoa plurality of segments, said ties controlling the flexing movementofsaid segments and preventing excessive enlargement of said grooves.

References Cited by the Examiner UNITED STATES PATENTS 879,471 2/1908Kabureck 135-64 2,661,041 12/1953 Walsh 152 209 3,040,757 6/1962 Smith135--64 FOREIGN PATENTS 963,349 12/1949 France.

10 HARRISON R. MOSELEY, Primary Examiner.

L. J. SANTISI, Assistant Examiner.

4. IN A FRICTION CRUTCH TIP, A BASE, THE GROUND ENGAGING BOTTOM SURFACEOF SAID BASE BEING SUBSTANTIALLY FLAT AND HAVING A PLURALITY OFCONCENTRIC NARROW GROOVES EXTENDING A SUBSTANTIALLY DISTANCE VERTICALLYUPWARDLY INTO SAID BASE FROM THE BOTTOM THEREOF, SAID GROOVES DIVIDINGSAID BASE INTO A PLURALITY OF SEPARATE CONCENTRIC LANDS SEPARATED FROMEACH OTHER BY SAID GROOVES, A PLURALITY OF TIES EXTENDING ACROSS SAIDGROOVES AND JOINING SAID LANDS, SAID TIES DIVIDING SAID LANDS INTO APLURALITY OF ARCUATE SEGMENTS, SAID TIES CONTROLLING THE FLEXINGMOVEMENT OF SAID SEGMENTS, AND PREVENTING EXCESSIVE ENLARGEMENT OF SAIDGROOVES, EACH OF SAID LANDS HAVING A PAIR OF EDGES, THE CORRESPONDINGEDGES OF A PLURALITY OF SAID LANDS BEING ADAPTED TO ENGAGE THE GROUNDUNDEPENDENTLY BUT SIMULTANEOUSLY WHEN SAID BASE IS FLEXED UPON THEPIVOTAL MOVEMENT OF SAID CRUTCH TIP, THEFRICTIONAL RESISTANCE OF THEBOTTOM OF SAID BASE TO SLIPPAGE COMPRISING THE SUMMATION OF THESIMULTANEOUS FRICTIONAL ENGAGEMENTS OF THE EDGES OF SAID LANDS WITH THEGROUND.